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It's difficult to imagine how life managed to survive in those circumstances. But survive it did. Microbiologist Online Radio believes that modern glaciers can tell us how it did so. She has come to the Columbia Icefield in the Rocky Mountains in search of organisms that are still able to endure such extremes today. The thing about being here is it looks like everything's been wiped clean, the glacier's come through and it's destroyed all life, there's nothing living. But to a microbiologist this looks a bit like a rainforest. From here you can see discolouration on the surface of the ice, but that's not dirt that is photosynthetic bacteria that are surviving there and that creates an ecosystem where you have plants and you have predators come in and feed on those organisms. So even though it looks dead, it's actually wildly alive with life. The kind of life you can see here is pretty ancient. They've had to adapt to a lot of global catastrophes. They had to adapt to Snowball Earth. Microorganisms that live in these harsh environments we call extremophiles. They have an amazing amount of adaptability that's hardwired in their genomes. You can freeze them, you can bury them a mile down in ice and its not much of a hindrance because of their adaptable nature. We owe our existence to icedwelling extremophiles. Snowball Earth almost extinguished life, but tiny organisms like these hung on for millions of years. I think what you had is organisms that could withstand extreme environments conditioning themselves to this changing ecosystem. You had a skin of microbes on the surface of the planet, and you had these organisms living between where the, the glaciers contacted the rock, and that was enough life trickling over so that when those conditions retreated, and it became more favourable, then it was like, pff, and everything took off again. Finally, Snowball Earth began to warm. There is evidence that around this time, there was a global surge in volcanic activity. Eruptions punched through the ice, spewing carbon dioxide into the air.